Population Growth and Resource Availability (3.5)

**Size (N)**

total # of individuals in a given area at a given time

larger size (N)

safer from population decline

**Density**

number of individuals/area

Higher density

higher competition, possibility for disease outbreak, possibility of depleting food source

**Distribution**

how individuals in a population are spaced out compared to each other

random: trees

uniform: territorial animals

clumped: herd/group animals

**Sex Ratio**

**ratio of males to females**closer to 50:50 ideal for breeding

die off or bottleneck effect can lead to to skewed sex ratio (not enough females) limiting pop. growth

**Density-Dependent-Factors**

factors that influence population growth based on size

Examples

food

light

competition for habitat

water

disease

All these things limit population growth based on their size

**Density-Independent Factors**

factors that influence population growth independence of their size.

examples

natural disasters

floods

hurricane tornado

fire

It doesn’t matter how big or small a pop. is, natural disasters limit them both

**Ex. of Density-Dependent Factor**

**Food**is a density dependent factor. (also a limiting resource)When twice as much food was added to the dish, both species increased carrying capacity by about 2x

**Biotic Potential**Max potential growth rate with no limiting resources

May occur initially, but limiting resources (competition, food, disease, predators) slow growth, & eventually limit pop. to carrying capacity (k)

**Biotic potential**

exponential growth

**Logistic growth**

initial rapid growth, then limiting factors limit pop. to K

# Population Growth and Resource Availability (3.5)

**Size (N)**

total # of individuals in a given area at a given time

larger size (N)

safer from population decline

**Density**

number of individuals/area

Higher density

higher competition, possibility for disease outbreak, possibility of depleting food source

**Distribution**

how individuals in a population are spaced out compared to each other

random: trees

uniform: territorial animals

clumped: herd/group animals

**Sex Ratio**

**ratio of males to females**closer to 50:50 ideal for breeding

die off or bottleneck effect can lead to to skewed sex ratio (not enough females) limiting pop. growth

**Density-Dependent-Factors**

factors that influence population growth based on size

Examples

food

light

competition for habitat

water

disease

All these things limit population growth based on their size

**Density-Independent Factors**

factors that influence population growth independence of their size.

examples

natural disasters

floods

hurricane tornado

fire

It doesn’t matter how big or small a pop. is, natural disasters limit them both

**Ex. of Density-Dependent Factor**

**Food**is a density dependent factor. (also a limiting resource)When twice as much food was added to the dish, both species increased carrying capacity by about 2x

**Biotic Potential**Max potential growth rate with no limiting resources

May occur initially, but limiting resources (competition, food, disease, predators) slow growth, & eventually limit pop. to carrying capacity (k)

**Biotic potential**

exponential growth

**Logistic growth**

initial rapid growth, then limiting factors limit pop. to K